Calcareous deposits form due to Impressed Current Cathodic Protection systems used to prevent corrosion of Navy vessel hulls and shafting. The deposits are a crystalline formation of calcium carbonate and magnesium hydroxide that form due to a local PH change on the protected surface. The area of concern is the section of shaft that contacts seawater lubricated propulsion bearings. During periods of inactivity, while in port, the shaft may sit stationary for long periods allowing the deposits to accumulate. The deposits are thought to cause abrasive wear when large amounts are present, and the shaft is actuated to turn at lower speeds.
Current shipboard practices vary widely for attempting to minimize the amount of calcareous deposits that build up on propulsion shafts. Currently there is no known test apparatus to test the significance of deposits on bearing and shaft life. Little to no scientific evidence is available to determine if the wiping of deposits is successful and if the operation is completed often enough. Thus, it is desired to have an apparatus and method for evaluating the effects of calcareous deposits on ship propulsion shafts, and also possible arrangements and methods for removing these deposits.